<textarea wrap=hard> does not match implementations

[annevk]

The specification suggests that the cols attribute is used for width when doing forced wrapping, but implementations (Chrome/Safari) use the rendered width (and wrapping) of text.

This came out of #6647. E.g., add style=display:none to the textarea in https://software.hixie.ch/utilities/js/live-dom-viewer/saved/9245 or style=width:1000px.

If that issue is solved by changing the wrapping to LF, as suggested, this issue can be used for remaining cleanup:

• Moving wrap=hard semantics into construct the entry list as the textarea element itself doesn't care about the result
• Redefining wrap=hard to exclusively use the rendered width (and not perform wrapping when nothing is rendered)
• Deduplicating API value into value
• Figure out what roles cols and rows play other than being presentational hints. (And maybe also clarify their relationship with the rendering section.)

[andreubotella]

For context, the WPT test at /html/semantics/forms/the-textarea-element/wrap-enumerated-ascii-case-insensitive.html passes in Chrome/Edge but not on Safari because Chromium's UA style sheet has <textarea>s use a monospace font and WebKit's doesn't.